There has always been the desire to know whether a door, drawer, or window has been opened. A returning resident often questions whether an unwelcome intruder is lying in wait or has been inside the house or apartment. Similar questions are: has the safe or other private enclosure been opened? Has the landlord been in the apartment without asking? These questions relate not only to forced entry but to any entry including entry with the use of a valid key.
Crude mechanical indicating devices have long been used. For example, a feather placed on the top edge of the door as it is closed will, hopefully, fall to the floor when the door is opened and remain there until the resident returns giving an opened-door indication. Certainly, many other inconvenient and unreliable indicators come to mind.
The art shows many door-security devices. Many devices are used for activating alarm systems. Others are designed for detecting the presence of invalid keys. There seem to be no devices designed for the specific purposes of the invention here.